Processes for the catalytic polymerization of the above-mentioned olefins are well known. One process of particular interest here is that described in U.S. Pat. No. 3,347,840, incorporated by reference herein. This patent raises the problem of the disadvantageous production of appreciable amounts of 1-hexene in the polymerization of ethylene, and suggests various compounds to counter or inhibit this unwanted trimerization, which detracts from the efficiency of the conversion to polyethylene.
It was apparent, however, that the catalyst utilized in the process, e.g., a chromium (III) salt, usually an alkanoate, in combination with a partially hydrolyzed aluminum alkyl, such as triisobutyl aluminum, was capable of producing 1-hexene, albeit in minor amounts, for example, ten to 20 percent by weight of the ethylene consumed, and much of the 1-hexene was incorporated into the polymer. This observation suggested that the ethylene polymerization catalyst could be used to trimerize ethylene in greater than the minor amounts mentioned provided that, instead of 1-hexene inhibitors, 1-hexene promoters could be found. In this vein, the above patent alludes to components, such as dimethoxyethane, which tend to increase the amount of ethylene converted to 1-hexene. There is no indication that the conversion would be at all efficient, however, and, in fact, following the teachings of the patent, it is not.